Soil-cement Mixtures Research Articles

Influence of Soil-Cement Composition on its Selected Properties

The paper discusses the results of mechanical and technological tests of soil-cement composites made with cohesive soil. The compositions of analysed soil-cement mixtures differed in terms of their cement paste volume fractions and water-cement ratios. Limiting values of these technological parameters that enable the application of the soil-cement mixtures obtained in real life conditions for the purposes of the Deep Soil Mixing (DSM) method were determined. Based on the test results obtained, it was found that mechanical properties of the materials analysed were very sensitive to changes in their compositions. Variations in the volume fraction of cement paste within the range analysed caused mechanical properties to change even by an order of magnitude.

Preliminary results of dry Deep Soil Mixing soil-cement composite testing

This paper provides results of testing made for soil-cement mixtures in dry mixing technology. This technology is greatly dependent on existing soil condition; hence the results are of highly random nature. Material used in testing was distinguished with high organic content and low humidity. Tests were carried out in laboratory of Wroclaw University of Technology on 145 samples as ordered by Menard Polska Ltd. Company. Samples were prepared and stored under laboratory conditions and then, after various maturation time, were destroyed in a testing machine. The purpose was to determine the stress-strain curves used to find strength properties, strain at failure, modulus of elasticity, secondary modulus of elasticity versus cement content. Test confirmed improvement of soil strength properties after addition of cement binder. The results may be used to determine the most economic binder-to-soil ratio.

Durability of Soil-Cement Blocks with the Incorporation of Limestone Residues from the Processing of Marble

The great environmental impact caused by mineral production has forced mining and ornamental stone industries to acquire new concepts and technical solutions in order to develop eco-friendly and sustainable activities. In this context, this work aims to study the durability of soil-cement block with the incorporation of limestone residues from the processing of marble as an ornamental stone. Specimens were prepared with 30, 40 and 50 vol% of residues added to the soil-cement mixture and analyzed for their physical, chemical and mineralogical properties. After the curing period, the specimens were subjected to mechanical analysis and the established experimental program showed that the addition of residues in the mixture becomes feasible for the preparation of soil-cement blocks, exhibiting improved results when compare to a reference block without residues.

The appliance of prefabricated soil-cement slabs processed with a hydrophobizing material for the road construction

The paper presents a complex method for increasing water resistance and reducing crack formation by using a prefabricated foundation of soil-cement slabs with surface processing with a hydrophobizing material on basis of organosilicon compounds. Theoretical, laboratory and full-scale experimental studies were made. Theoretical studies are based on the substantiation of the geometric parameters of the slab in order to exclude the probability of its destruction under its own weight during building and installation works. The result of the first stage of laboratory studies is the determination of the optimum composition of soil-cement mixture in order to achieve a grade of strength M20. At the second stage, the effectiveness of the influence of hydrophobizing materials "Tiprom U" and "Penetron-Admix" on water absorption and compressive strength of soil-cement was determined. The final stage of the research was a full-scale experiment. In the factory environment, soil-cement slabs were manufactured in metal forms. Based on the results of the research, conclusions about the effectiveness of this complex method were made. The use of soil-cement slabs allows reducing crack formation, as well as to work all year round due to manufacturing and surface treatment of slabs in the factory conditions.

Efeito da umidade inicial e do tempo de cura nas propriedades mecânicas de misturas solo-cimento

Misturas de solo-cimento são muitas vezes empregadas como material de base ou sub-base para pavimentação em locais com pouca disponibilidade de agregados. O processo de dosagem comumente empregado no Brasil consiste na verificação de um valor de resistência à compressão simples mínima aos 7 dias de cura. O procedimento convencional de mistura em laboratório consiste em incorporar cimento ao solo na umidade higroscópica e, posteriormente, a água para compactação. Comparou-se este procedimento com a técnica que simula a condição de construção que consiste na mistura do cimento ao solo na umidade de coleta na jazida. Foram compactados corpos de prova por impacto e realizados ensaios de Módulo de Resiliência (MR), Resistência à Compressão Simples (RCS) e Resistência à Tração por Compressão Diametral (RTCD) para quatro tempos de cura (7, 14, 21 e 28 dias). Os resultados apontaram a influência da umidade inicial de mistura nos parâmetros volumétricos e mecânicos das misturas de solo-cimento. As deflexões de um trecho experimental com base de solo-cimento também foram avaliadas para comparação do módulo de resiliência obtido por retroanálise com os dados obtidos em laboratório. Os valores de módulo de resiliência da camada de solo-cimento em campo são inferiores comparados aos dados obtidos em laboratório, podendo ter sido ocasionado por início do processo de microfissuração da base cimentada, além de fatores executivos. Pode-se ainda somar a esse fator, a forma como a umidade é ajustada em laboratório e em campo.

Study on strength estimation of soil cement used in the embedded pile method by electrical resistivity measurement

Problems caused by poor quality control and quality assurance of the pre-boring embedded pile construction, such as on domestic apartment house is still occurring nowadays. An adequate consideration for invisible risks inside or below the ground is important in pile foundation construction therefore the demand for advanced and reliable quality assurance is increase in the future. In this research, to understand the quality of the construction at early stage, the compressive strength of cement-soil mixture of pile construction after 28 days is estimated using electrical resistivity value of the mixture. More accurate measurement for electrical resistivity value is conducted by inserting the electrodes without using potassium chloride solution as a catalyst. The result showed that there is a certain tendency in the electric resistivity value at the early age regarding to the type of soil (sand, clay) mixed in. The most accurate estimation was achieved from the electric resistivity value at the first day and several days onwards, and from the compressive strength after 3 days.

Deep mixing method for the construction of earth and water retaining walls

In the deep mixing method, the ground is mechanically mixed in place while a binder, often based on cement, is injected. After hardening of the soil-cement mixture, called soil mix material, soil mix elements are formed in the ground. Originally known as a ground improvement technique, the deep mixing is more and more applied for the construction of earth-water retaining structures within the framework of excavation works. 
 After a short introduction to the execution aspects of the method, the authors discuss the hydro-mechanical properties of the soil mix material mainly based on the results of the BBRI Soil Mix project (2009-2013). A design approach dedicated to the soil mix retaining walls and developed in collaboration with the SBRCURnet is then presented. In this methodology, which is in line with the structural Eurocodes, design rules are adapted to the functions of the soil mix wall (earth-water retaining, bearing and cut-off functions) including the temporary or permanent character of the application. Based on the result of large-scale bending tests, the interaction between the soil mix material and the steel reinforcement is considered in the calculations allowing a reduction of the steel section between 10 and 40 %.

A general relationship to estimate strength of fibre-reinforced cemented fine-grained soils

Fibre addition and Portland cement treatment are used to amend the adverse characteristics of some fine-grained soils and to enhance their mechanical properties. The present study proposes a single power function that quantifies the effects of the amount of cement and porosity on the unconfined compressive (qu) and split tensile (qt) strength of fibre-reinforced fine-grained soil-cement mixtures. The practical value of the equation is that only one unconfined compression (or split tensile) test of a specimen moulded with a specific fibre type, fibre amount, specific cement amount, porosity, and cured for a given time period is required to estimate the strength of the fibre-cement soil mixture. The equation can be used for a wide range of porosities and cement contents, and for other fibre-reinforced fine-grained soils treated with cement.

English

The study evaluated the chemical stabilization of soils with cement toward application in improving forest roads, as constructive alternative of low cost. The study was carried out with fine soils from the region of Niquelândia-GO, where the sand-clay-silt particle proportion was predominant, and Portland cement CP-II-Z-32 used as a stabilizing agent at 2% under dry soil weight. Geotechnical tests were conducted in different compaction energies (normal, intermediate and modified) and curing periods (1, 7 and 28 days), and the data were analyzed statistically by Analysis of Variance (ANOVA) and Tukey test. The soil-cement mixture presented higher unconfined compressive strength (UCS) than the compacted local soil, reaching a highest value of 650.52 kPa on modified compaction energy. Also, California bearing ratio (CBR) with values ​​of 44.1% in the intermediate compaction energy and 41.7% in the modified compaction energy reached higher values compared to lateritic soil sampled. Soil-cement mixture was prescribed as improved layer for forest road surface, as well as reached indication for subgrade reinforcement material and sub-base in conventional paved roads.   Key words: Forest management, chemical stabilizing, lateritic soil, unpaved roads.

Three point bending flexural strength of cement treated tropical marine soil reinforced by lime treated natural fiber

Marine soil in the Selangor State of Malaysia was characterized with respect to its engineering properties as pavement layer in road constructions. Samples were collected from North Klang area in Selangor, Malaysia and subjected to physico-chemical, mineralogical and geotechnical analyses. Quick lime or calcium oxide (CaO) treated coconut fibers were introduced to soil cement mixture to enhance the flexural strength of tropical marine soil. Three point bending tests were carried out on treated samples after 7, 14 and 28days respectively. The tests results showed improvements in the flexural performance of the mixture as it could be seen by the increase in the flexural strength, Young’s modulus and the toughness index especially when the treated fibers were incorporated into the mixture. It was found that, the bond strength and interaction between treated fibers and soil was the dominant mechanism controlling the reinforcement benefit. It can be concluded that, the application of the CaO treated coconut fiber reinforced cement treated marine clay from Peninsular Malaysia is useful both in strength and ductility as pavement layer in road constructions.

Bonding effect on the evolution with curing time of compressive and tensile strength of sand-cement mixtures

Soil-Cement mixtures are used in several geotechnical applications and consist of artificially structured materials with stable fabric due to the presence of artificial bonds, which are the hydrated cement minerals coating the aggregates (soil particles). An extensive experimental study was performed on samples of an artificially cemented silty sand prepared by adopting three different dosages of cement and different water-cement ratios for each dosage. Realistic values for the dosages and water-cement ratios were adopted considering soil-cement mixtures performed by compaction or by grout injection. The unconfined compressive strength (UCS) and indirect tensile strength (ITS) of the mixtures were measured for different curing times. The values found were related to the water-cement ratio adopted for the mixing process, because of the dependency between the porosity of cement and the geometry of the bond minerals observed in electron scanning microscope images. The bond geometry varied considerably depending on the amount of water used in the preparation, particularly in the case of low cement dosages. The definition of degree of bonding was adopted to describe the evolution along curing time of UCS and ITS considering the values measured after 3days of curing as reference points. This degree of bonding is useful for the definition of constitutive models for artificially structured materials. This parameter was indirectly related with the bond geometry; that is, the paths of strength evolution found were similar for samples with dispersed bonds. The improvement of tensile strength and compressive strength are correlated through a constant, independent of the dosage and water-cement ratios adopted for the mixture. Several authors have found identical values for this constant when studying compacted sand-cement mixtures. The particular structure resulting from the preparation process adopted does not affect this constant, however it affects the maximum UCS and ITS achieved for each cement dosage studied. This maximum depends on the water-cement ratio, and therefore this ratio is an important design parameter to be considered when prescribing compacted or grouted solutions.

Strength properties of epoxy resin–soil–cement mixtures

The use of new materials for soil strengthening is crucial for geotechnical engineering, especially in methods that are commonly used for ground improvement, such as deep mixing. The main objective of this study was to investigate the potential use of two-component water-soluble epoxy resins to improve the mechanical properties (compressive strength, splitting tensile strength, elastic modulus, shear strength parameters) of clay soils, because the efficacy of these resins on soil strengthening has not yet been properly investigated. The experiments were conducted using soil mixes with different epoxy resin-to-water ratios, solid-to-water ratios and cement content. The results of this study indicate that epoxy resin, when combined with cement, improves the mechanical properties of the clay soil significantly, and could provide a suitable solution for deep mixing method applications or other geotechnical operations. Based on the experimental results, a non-linear regression analysis was performed to correlate the mechanical properties of the mixes with epoxy resin, water, solid, cement content and curing time. The accuracy of the produced model was found to be satisfactory.

Influência do teor de umidade, da porosidade e do intervalo de tempo até a aplicação da mistura solo-cimento em pavimento rodoviário

Pretende neste trabalho avaliar a influência do teor de umidade, da porosidade e do intervalo de tempo até a aplicação, sobre a resistência à compressão simples (RCS) de misturas de solo-cimento. Foram realizadas três baterias de ensaios, usando misturas de solo-cimento compactadas, com 6 e 7 % de cimento. Na primeira bateria foi utilizada a umidade ótima (wótima) e energia Normal de Proctor, na segunda usou-se wótima + 1 % e energia Normal de Proctor e na terceira foi utilizada a wótima + 1 % e energia de compactação alterada, a fim de verificar a influência do teor de umidade. Para cada dosagem as compactações ocorreram em 10 intervalos de tempo até a aplicação, variando de 0 min a 6 h, com o intuito de verificar, no desempenho mecânico, a influência do intervalo de tempo até a aplicação do solo-cimento. Os resultados apon-taram que o aumento no intervalo de tempo até a aplicação diminui a RCS e este tempo é limitado para atingir a RCS mínima requerida de 21 kg/cm², variando conforme o teor de cimento, teor de umidade e energia de compactação. Quando a com-pactação se deu com wótima + 1 % foram obtidos maiores valores de RCS, para os mesmos tempos de aplicação. Em todas as dosagens verificou-se que quanto mais baixa a porosidade da mistura solo-cimento melhor foi o desempenho mecânico.

An Experimental Investigation on Effect of Adding Natural and Synthetic Fibres on Mechanical and Behavioural Parameters of Soil–Cement Materials

Soil–cement is a mixture of Portland cement, soil and water that sticks together due to the hydration of the cement and compression of its components to create a dense, durable compound, which has low permeability and is resistant to erosion. Unfortunately, these mixtures do not perform well under tensile load because soil–cement materials are brittle. In this study, three types of fibres were used to reinforce the materials to compensate for this flaw: jute (a natural fibre), polypropylene, and steel (a synthetic fibre) fibres. These fibres were randomly added to the soil–cement mixture in three percentages (1, 2, and 3%). Tests were then conducted on three different soil–cement gradations each with three fine contents of different mineral types (nine different gradations in total). First, sand equivalent and Atterberg limits were conducted on the soil samples. Then compaction, unconfined compression strength, indirect tensile strength and flexural tests were conducted on the soil–cement samples in two conditions: control (unreinforced) and reinforced soil–cement samples. Results showed an undeniable role of fibres in changing the behaviour of the soil–cement–fibre matrix from brittle to ductile producing post-peak behaviour. The results also show that compressive, tensile and flexural strengths of soil–cement materials improved dramatically by adding steel fibres to the matrix.

Influence of Water–Cement Ratio on the Hydraulic Behavior of an Artificially Cemented Sand

In general, the prescription of the amount of water used in soil–cement mixtures is done to define the optimal compaction conditions for bases and sub-bases, or to ensure the fluidity necessary for a good mixture by injection. A better knowledge about the hydraulic behaviour of the resulting mixtures may be useful in service conditions, when permeability is important or when the layers are exposed to wetting and drying cycles. The relationship between saturated hydraulic permeability, coefficient of water absorption by capillarity and water retention properties were investigated for an artificially cemented sand prepared with different and realistic cement dosages, and with different water–cement ratios for each dosage. The water–cement ratio was considered in the analysis because it affects porosity and pore size distribution of the cement paste, and consequently tortuosity. Low values of this ratio mimic compacted sand–cement mixtures and large values simulate grouted sands. The dosages adopted simulate those used in pavement layers and obtained in grouted bodies. The results of an extensive set of experimental tests, performed to determine the hydraulic properties mentioned, are interpreted in the paper considering the presence and structure of the hardened cement paste. The materials prepared with low water–cement ratio have higher permeability and different water retention properties from those prepared with high ratios. Nevertheless, the water used in the hydration of the cement also affects the porosity and tortuosity of the hardened paste and may increase porosity if grout is very fluid. This study contributes to increase the knowledge about the effects of design parameters cement dosage and water–cement ratio on the hydraulic behaviour of the mixtures, which may be relevant when evaluating water retention and percolation.

Physicochemical and consolidation properties of compacted lateritic soil treated with cement

The consolidation of a fine-grained lateritic soil, treated with compound Portland cement (CEMII/BM 32.5N) up to 9% by weight of the dry soil and prepared at three different molding water contents (ωDRY, OMC, and ωWET), was investigated by means of a one-dimensional consolidation test. The physicochemical and microstructural properties of the compacted lateritic soil-cement mixture were investigated using Raman spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), and pH measurement. The results show that cement admixtures resulted in the formation of tobermorite, afwillite, ettringite, portlandite, and calcite. However, tobermorite and afwilite, which are calcium silicate hydrates (CSH) whose mechanisms of formation are the pozzolanic and alkali silica reactions, appear from 6% added cement. The fixing point of the pH (12.4) is also obtained from 6% added cement. It is the threshold value at which the material begins to develop an adequate mechanical performance. In general, as the content of cement in the soil is increased, the yield stress increases from 1 to 3 times in comparison to untreated soil. For effective vertical stresses smaller than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is 2–7 times faster than that for specimens not treated with cement, while for effective vertical stresses higher than the cement-induced yield stress, the primary consolidation process for specimens treated with cement is about 0.5–1.5 times faster than that for specimens not treated with cement. Permeability and secondary compression are reduced 1–9 times and 2–11 times that of the untreated samples, respectively. These changes are attributed to the creation of chemical bonds and aggregation that accompany the addition of cement. The results also show that it would be desirable for soil samples to be prepared at the dry side of optimum (ωDRY) when the optimum moisture content (OMC) is not reached at the site. These results indicate that significant and desirable changes in soil behavior can be achieved when the soil is admixed with CEM II/BM 32.5N cement, thus providing the possibility of using the tested lateritic soil in road construction.

About the Possibility of Applying Coloured Soil-Cement in Making Road Pavement Layers

The issue of the urban environment decoration has continuously been the task of urban architecture authority and it is quite successfully performed. Adding pigments, using coloured filler in the content of bitumen-concrete mixtures or applying multi-coloured paving stones and mosaic rigid concrete pavements provide additional positive impression in the perception of intra-buildings space and modern urban landscape. The use of local materials with adding pigments for the design of residential areas can be extremely important for local communities.In order to test soil-cement mixtures with added colour pigment for road pavements on the basis of construction laboratory at Lutsk NTU, a series of experiments has been planned to answer the question of the pigment amount impact on the physical and mechanical properties of the materials and finding the best ratios for them.

Hydraulic Conductivity of Residual Soil-Cement Mix

In Malaysia, although there are several researches on engineering properties of residual soils, however study on the hydraulic conductivity properties of metasedimentary residual soils is still lacking. Construction of containment walls like slurry wall techniques can be achieved with hydraulic conductivity of approximately 5 x 10-7cm/sec. The objectives of the study were to determine the physical properties of metasedimentary residual soils and to determine the influence of 1%, 3%, 5% and 10% of cement on hydraulic conductivity parameters. The coefficient of hydraulic conductivity of the soil naturally and soil-cement mixtures were determined by using the falling head test. According to the test, the hydraulic conductivity of the original soil was 4.16 x 10-8 m/s. The value decreases to 3.89 x 10-8 m/s, 2.78 x 10-8 m/s then 6.83 x 10-9 m/s with the addition of 1%, 3% and 5% of cement additives, respectively. During the hydration process, cement hydrates is formed followed by the increase in pH value and Ca(OH)2 which will alter the modification of pores size and distribution. When the quantity of cement increases, the pores size decrease. But, the addition of 10% cement gives an increased hydraulic conductivity value to 2.78 x 10-8 m/s. With 10%, the pore size increase might due to flocculation and agglomeration reaction. The generated hydraulic conductivity values will indirectly become a guide in the preliminary soil cement stabilization to modify the properties of the soil to become more like the properties of a soft rock.1. Introduction

Long Term Cyclic Response of a Soil-Cement Mixture: Experimental Study and Modelling

Soil and granular materials stabilization with hydraulic cements is an interesting solution as stiffness and strength are highly improved. It is especially attractive when high traffic loads with considerable number of passages are expected and high mechanical properties of subgrade soils are required. Furthermore, such improvement allows reducing the amount of natural soils to be disposed for the fact of being rehabilitated, with significant environmental and economic advantages. Many authors have studied the cyclic behaviour of soils and soft rocks and others have studied soil-cement mixtures under static conditions. However, few studies have been published on soil-cement mixtures in cyclic conditions, particularly with a high number of cycles.The purpose of this paper is to analyse the behaviour of some mixtures of cement-treated soil subjected to long term cyclic loading in order to contribute to the identification of rational criteria for design of subgrades for transportation infrastructures. The soil used is a well-graded silty sand remoulded from the weathered horizons of Porto granite, the most common rock in the north-western region of Portugal. The cement added to the soil varied in four percentages from 0 to 7% of mass of the uncemented soil. For each of these cement contents, two specimens were moulded with two initial void ratios. The study included an extensive set of long-duration drained cyclic triaxial tests, performed under stress-controlled conditions using an automatic hydraulic system with cells containing high-precision internal axial and radial strain gauges.The scope of the triaxial cyclic tests is to study the evolution of the accumulation of permanent strain in cemented and uncemented specimens subjected to cyclic loading.

Influence of Water Content in the UCS of Soil-Cement Mixtures for Different Cement Dosages

Soil-Cement mixtures are artificially structured materials with stable fabric due to the presence of artificial bonds. This type of materials is used in several geotechnical applications such as in pavement base layers in transportation infrastructures. In this paper artificially cemented silty sands are studied adopting dosages of 10% and 13% of Portland cement (by weight of dry soil). In order to analyze the impact of the molding water content in the Unconfined Compressive Strength (UCS) of the mixtures through time, the mixtures were prepared for water to cement ratios varying between 0.6 and 2.0 and tested for different curing periods (3, 7, 14 and 28 days). UCS test results are interpreted considering the presence of bonds connecting the grains. The definition of a bonding parameter is adopted aiming to quantify the improvements achieved for the different cases investigated and considering curing periods.